On Tue, May 09, 2017 at 12:06:29AM +0900, Akira Yokosawa wrote: > On 2017/05/07 20:50:15 -0700, Paul E. McKenney wrote: > > On Sun, May 07, 2017 at 09:23:03AM +0900, Akira Yokosawa wrote: > >> On 2017/05/03 07:59:48 -0700, Paul E. McKenney wrote: > >>> On Wed, May 03, 2017 at 05:14:57PM +0900, Akira Yokosawa wrote: > >>>> On 2017/05/02 19:47:19 -0700, Paul E. McKenney wrote: > >>>>> On Wed, May 03, 2017 at 09:23:11AM +0900, Akira Yokosawa wrote: > >>>>>> On 2017/05/03 09:09:37 +0900, Akira Yokosawa wrote: > >>>>>>> Hi Paul, > >>>>>>> > >>>>>>> While reviewing your recent update in "Hunting Heisenbugs" section, > >>>>>>> I found the analogy with particle physics didn't sit well with me. > >>>>>>> > >>>>>>> "Heisenbug" is defined as: > >>>>>>> > >>>>>>>> attempts to track down the heisenbug causes it to radically change > >>>>>>>> its symptoms or even disappear completely. > >>>>>>> > >>>>>>> "Anti-heisenbug" is introduced as: > >>>>>>> > >>>>>>>> Fortunately, particle physics is up to the task: Why not create > >>>>>>>> an anti-heisenbug to annihilate the heisenbug? > >>>>>>> > >>>>>>> At this point, "anti-heisenbug" seems to mean a patch that fixes > >>>>>>> the heisenbug. > >>>>>>> > >>>>>>> The use of anti-something in particle physics does not go along > >>>>>>> with this usage. > >>>>>>> > >>>>>>> For example, antiproton is an antiparticle of proton. > >>>>>>> antiproton has mostly the same property as proton, > >>>>>>> with the exception of electric charge and magnetic moment. > >>>>>>> Also, an antiproton and an antielectron (positron) can compose > >>>>>>> an antihydrogen atom. Well, I'm sure you know all about this. > >>>>>>> > >>>>>>> So, if you employ this line of reasoning, an anti-heisenbug should > >>>>>>> also be a bug with something opposite in nature. > >>>>>>> > >>>>>>> If a heisenbug is a bug which vanishes when it is being tracked down, > >>>>>>> an anti-heisenbug would be a bug which only emerges when it (or > >>>>>>> something else) is being tracked down. > >>>>>>> > >>>>>>> However, it is not obvious you can create an anti-heisenbug for > >>>>>>> a particular heisenbug so that when the two are combined, the symptoms > >>>>>>> of both bugs to "annihilate". > >>>>>>> > >>>>>>> So I'm wondering "What was Paul's intention in using the word 'annihilate'?". > >>>>>>> > >>>>>>> In Section "Add Delay", anti-heisenbug is used as: > >>>>>>> > >>>>>>>> Once you spot a bug involving a race condition, it is frequently > >>>>>>>> possible to create an anti-heisenbug by adding delay in this manner. > >>>>>>> > >>>>>>> This "anti-heisenbug" is not a bug, rather, it is a means to increase > >>>>>>> the possibility of a given heisenbug to appear. > >>>>>>> > >>>>>> > >>>>>> Oops, I sent this prematurely. > >>>>>> But you might be able to see my point here. > >>>>>> > >>>>>> This is not an important question, so please give it a look when you have > >>>>>> done with whatever issue you are working on. > >>>>> > >>>>> I freely admit that I am taking a fair amount of "poetic license" here. ;-) > >>>> > >>>> So, what about adding a footnote like this? > >>> > >>> That isn't bad at all! > >>> > >>> But let's take a look at several possible approaches: > >>> > >>> o Continue using "anti-heisenbug", but remove the current definition. > >>> (To the extent that it could be considered to be a definition.) > >>> > >>> o Use the following analogy: > >>> > >>> When you annihilate an electron and a positron, you don't > >>> get nothingness, you instead get an energetic photon. > >>> Similarly, when you annihilate a heisenbug and an > >>> anti-heisenbug, you don't (usually) get nothingness, > >>> instead, you get a (hopefully) easier-to-locate bug. > >>> > >>> o The solution you propose below. > >>> > >>> o Leave as is, and assume that people will get the "poetic license". > >>> > >>> o Additional ideas here! > >>> > >>> o Any of the above, but have a quick quiz on the definition > >>> instead of a footnote or an inline definition/explanation. > >>> > >>> Thoughts? > >> > >> I looked around the use of "heisenbug" and found an entry in quora: > >> > >> https://www.quora.com/Why-do-people-mix-up-the-observer-effect-and-the-uncertainty-principle > >> > >> What "heisenbug" should imply is the "observer effect", not the "uncertainty principle". > >> > >> So the definition of heisenbug given in the text is already confusing. > > > > That may be, but I wasn't the one who defined heisenbug. ;-) > > > > But given that it is defined, and given that a very large number of people > > are very scared of heisenbugs, it is my job to reduce, preferably remove, > > the fear. Less fear is needed so that they can better deal with the > > heisenbugs that they will inevitably come across. > > > >> An example of observer effect in quantum mechanics is interference of > >> electron beam passing through double slit. > >> If you don't know which slit each electron passes, you can observe interference > >> pattern. But once you put some equipment to know which slit an individual > >> electron passes, you no longer see the interference pattern. > >> > >> This situation is much relevant to heisenbug, isn't it? > > > > Well, it actually -might- be possible to come up with a heisenbug that > > mimicked quantum superpositioning and entanglement, but I don't know of > > one right offhand. Actually, it -has- to be possible to generate such a > > heisenbug because we can simulate quantum systems with software. Whether > > or not such a heisenbug would actually occur naturally, I couldn't say. > > Seems a bit unlikely, but then again, so did RCU. ;-) > > Hmm, hard to imagine... So was RCU. ;-) > >> Heisenberg used observer effect to explain his uncertainty principle as > >> a thought experiment on the gamma-ray microscope. > >> This is the origin of the confusion. And most people are still confused. > >> > >> So I don't like to see further analogies with misleading implications, which > >> would just look odd or strange for those familiar with particle physics who > >> happens to be also interested in parallel processing. > > > > The readers need to laugh enough, be confused enough, or whatever, in order > > to let go of their fear. > > ;-) > > > > >> All we need is to *somehow* make (the symptom of) a given heisenbug be > >> reliably reproduced. And those "somehow"s are the theme of this section. > > > > That is true! > > > >> So, I'd suggest 1) fixing the definition of heisenbug, 2) departing from > >> the analogy of particle physics. One problem is what name to use instead of > >> anti-heisenbug. If you use "anti-" as in "antibiotics", anti-heisenbug > >> is not necessarily confusing. > > > > I am not at all optimistic about being able to fix the definition > > of heisenbug. It has been in use for far too long. > > And most people are likely to have heard of the uncertainty principle. Exactly! > >> Or you might be able to come up with a better analogy by looking into studies > >> in quantum measurement such as "weak measurement". This field is related to > >> quantum computing you are planning to include into perfbook. > >> > >> See e.g. http://iopscience.iop.org/article/10.1088/0031-8949/91/7/073001/meta > >> > >> This is a review paper written from experimenters' POV, and should be easier > >> to read than theoretical papers cited therein, I suppose. > > > > But if we have to educate the typical reader about weak measurement, we > > have already lost. > > Point taken. > > > We will lose them, and they will retain their > > crippling fear of heisenbugs. > > > > How about something like the following patch? > > Fair enough. > > And "heisen-ness" sounds funny enough. > > If you want to add, > > Acked-by: Akira Yokosawa <akiyks@xxxxxxxxx> Added and pushed, thank you! Thanx, Paul > Thanks, Akira > > > > > Thanx, Paul > > > > ---------------------------------------------------------------------- > > > > commit 50d1f21f54540ff6ec38cc44715c213c3e16f2fe > > Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > > Date: Sun May 7 20:46:19 2017 -0700 > > > > debugging: Add footnote stating that "heisenbug" is a misnomer > > > > https://www.quora.com/Why-do-people-mix-up-the-observer-effect-and-the-uncertainty-principle > > http://iopscience.iop.org/article/10.1088/0031-8949/91/7/073001/meta > > > > But the word is well entrenched in common usage in parallel programming. > > > > Reported-by: Akira Yokosawa <akiyks@xxxxxxxxx> > > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > > > > diff --git a/debugging/debugging.tex b/debugging/debugging.tex > > index e621ebdb540b..c41057f35c31 100644 > > --- a/debugging/debugging.tex > > +++ b/debugging/debugging.tex > > @@ -1370,23 +1370,30 @@ The next section discusses counter-intuitive ways of improving this situation. > > > > This line of thought also helps explain heisenbugs: > > adding tracing and assertions can easily reduce the probability > > -of a bug appearing. > > -And this is why extremely lightweight tracing and assertion mechanism are > > +of a bug appearing, which > > +is why extremely lightweight tracing and assertion mechanism are > > so critically important. > > > > -The name ``heisenbug'' stems from the Heisenberg Uncertainty Principle > > -from quantum physics, which states that it is impossible to exactly > > -quantify a given particle's position and velocity at any given point > > -in time~\cite{WeinerHeisenberg1927Uncertain}. > > +The term ``heisenbug'' was inspired by the Heisenberg Uncertainty > > +Principle from quantum physics, which states that it is impossible to > > +exactly quantify a given particle's position and velocity at any given > > +point in time~\cite{WeinerHeisenberg1927Uncertain}. > > Any attempt to more accurately measure that particle's position will > > result in increased uncertainty of its velocity. > > -A similar effect occurs for heisenbugs: attempts to track down the heisenbug > > -causes it to radically change its symptoms or even disappear completely. > > +A roughly similar effect occurs for heisenbugs: attempts to track down > > +the heisenbug causes it to radically change its symptoms or even disappear > > +completely.\footnote{ > > + The term ``heisenbug'' is a misnomer, as most heisenbugs are > > + fully explained by the \emph{observer effect} from classical > > + physics. > > + Nevertheless, the name ``heisenbug'' has stuck.} > > > > If the field of physics inspired the name of this problem, it is only > > -logical that we should look to the field of physics for the solution. > > +logical that the field of physics should inspire the solution. > > Fortunately, particle physics is up to the task: > > Why not create an anti-heisenbug to annihilate the heisenbug? > > +Or, perhaps more accurately, to annihilate the heisen-ness of > > +the heisenbug? > > > > This section describes a number of ways to do just that: > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe perfbook" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
